Prior art of possible relevance includes the following U.S. Pat. Nos.: 2,497,177 issued Feb. 14, 1950 to McClintock et al; 2,780,361 issued Feb. 5, 1957 to Evans; 3,688,909 issued Sept. 5, 1972 to Titus et al; and 4,166,036 issued Aug. 28, 1979 to Barnhouser.
In U.S. Pat. No. 2,418,950 there is described a clarifier for waste water that has met with substantial success and has been recognized as one of the most efficient clarifiers or settling tanks devised. In practice, such a clarifier is constructed with a generally circular vessel which receives the waste water to be treated. Just inwardly of the side wall is a peripheral skirt which extends about the side wall from a waste water treatment inlet almost a full 360.degree. to a scum outlet. Typically, the spacing between the skirt and the side wall progressively narrows as one moves from the inlet to the scum outlet.
The lower end of the skirt is located above the bottom wall of the vessel.
The progressive narrowing of the space between the skirt and the vessel wall causes influent to be forced under the bottom of the skirt and rise into the center of the vessel. Solids within the influent settle in the process and accumulate on the bottom of the vessel.
Centrally of the vessel is a weir structure which serves as an effluent collecting trough. Clarified waste water at the water level in the vessel flows across the weir structure to be collected and discharged as clarified effluent. The flow of water in the vessel is circular with constant radially inward movement toward the collecting trough.
Though this clarifier works well for its intended purpose, occasionally difficulties may be encountered where the water to be treated contains considerable scum which accumulates on the surface inwardly of the skirt. In such a case, such scum may flow across the weir at the effluent collector to be discharged with the effluent. Since the effluent is intended to be clarified when discharged, the presence of such scum may result in a perception of a less than fully efficient clarifying operation.
Scum skimming apparatus has been employed in other waste water treatment apparatus as well. In many cases, the skimming apparatus is cumbersome and/or expensive to fabricate.
The present invention is directed to overcoming one or more of the above problems.